Sorry I just couldn't resist. But I think this is a cool question and I am courious about the answer. Now thanks to this wonderful forum I will be ntified via email as soon as someone with answer comes along.
Now back to this wonderful thread.
There's a code on the side of the pots. They all start with 137 which means it's unstacked. The next two numbers indicated the year it was made. The last two numbers indicate the week of that year.
Example:
1377726 indicates an unstacked pot made during the 26th week of 1977...ie June 1977.
1377852...52nd week of 1978...ie Dec 1978.
As Music Man purchased them in large quantities, it's not unusual to find pots older than the Basses. My 79 'Ray (from memory) has a couple of 1978 pots and a 1977 pot.